Looking for a military novel where the protag starts as a simple/commoner man like "I am the Monarch". It has few chapters so I'm craving for more. I've read RTW and it kinda fits the bill. I love that sense of growth of a kingdom/monarch feeling. Road to Kingdom had a good premise but sadly it went to path I don't particularly enjoy (excessive explicit content). New to WN/LN in general. Cheers!
Heavenly Jewel Change. Well it is not a military novel but there are 2 arcs in that the mc train in the army and develop a whole military so you might like. One is right at the beginning so you can see quickly if it is to your taste.
I haven't read either any of the novels that you mentioned as examples but one good example of a novel with strong military themes and a character who starts as a commoner is Akuyaku Reijo Ni Koi Wo Shite which I highly recommend.
Counterfeit Hero But qidian only translated ~110 out of 900+ chapters, so if you want to finish it, it's MTL or GTL for you.
Forty Millenniums of Cultivation. MC starts as a slum brat and grows into a refiner/all rounder cultivator. Military focus of the story is far lower than I am the Monarch, but still significant. Story starts as MC living in the slums and managing to send himself to a decent high school. After school arc & a follow up arc, MC goes to one of the Cultivation University's to study Refining (Cultivation Tool Creation). The Cultivation Universities are also military schools, though they each have different specializations, as Cultivators are socially and legally required to assist in military endeavors, particularly on the defensive front. MC fights in a battle, and, eventually (quite a while later), ends up joining the military for a while. Then things happen and the MC stops working directly with the army, and it's up to where the translation is right now. Purposefully vague as to not give major spoilers, while trying to give enough information for the OP to decide if this story is what they want or not.